The present invention relates to electronic circuits and more particularly to a low pass filter circuit.
It is well known that electrical circuits, such as sensing circuits, generate noise, an obviously undesirable but seemingly inevitable situation. Significant efforts have been undertaken either to reduce or to mitigate the undesirable effects that noise can cause in an electrical circuit. One way is to with an amplifying and filtering circuit that has a single-ended input and a single-ended output. This circuit uses an amplifier that receives a single-ended input signal, implements a sample and hold operation alternately on each of the amplifier inputs achieved by alternately switching switches on each of the amplifier inputs. When a first switch on one of the amplifier inputs is closed, the amplifying and filtering circuit samples a first signal having a noise component. The first switch is opened and a second switch on a second one of the amplifier inputs is closed, thereby allowing the amplifying and filtering circuit to sample a second signal having a desired output component and a correlated noise component. The second switch may then be opened. The first signal is subtracted from the second signal to allow recovery of the desired output component minus correlated noise.
The above technique, while providing acceptable low pass and noise filtering performance is, however, not without its limitations. Accordingly, it would be advantageous to provide new filtering techniques that improve upon the afore-disclosed technique and circuit.